5.7 Crank Tight Spot

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moparspares

moparspares

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I put the crank in this engine and torqued it all down. i could turn the crank by hand however it just felt a little tight in one spot. I could still turn it by hand but it felt like it was grabbing slightly. I pulled it all apart and inspected the bearings and there was no obvious scuffing so I recleaned everything and tried again. This time I torqued it to only half - 50ft lbs and spun it by hand again and same grabbing in one spot but less pronounced.

I am using ARP studs and I didn't line hone so could this be causing my issue. In saying this the caps mated together quite easily with a slight tap.

When I pulled this engine apart a couple years ago it did have a spun bearing but I cant remember which main. Not sure if it was an existing issue from the spun bearing or an issue with not line honing with the studs. Any thoughts
 
I'm Not Qualified on that, other to say, that's an Issue! BUT I WIIL SAY,
one ( or more) of the Brother Members here will Definitely get you looking the Right Way, and Help get You Properly Diagnosing and Solving it! GREAT PEOPLE HERE!!
 
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I have switched to studs and not had to line hone/bore. The snag is you said it had a spun main before. You'll definitely need to take it to a shop and have it fixed.
 
Lightly torque all bearings and then Torque 1 bearing at a time to see where the offending tight spot is.
 
Did you torque the caps in place without the crank in it and measure for bearing clearance or an out of round cap? What are the clearances?
 
tonysrt said:
Lightly torque all bearings and then Torque 1 bearing at a time to see where the offending tight spot is.
Click to expand...

Another thing you could try is just setting the crank in the block without caps using upper bearing shells only in first and last saddles. Rig up a dial indicator and check for run out at other main journals.

Bent crank could be the reason for the spun bearing.
 
I've had a similar issue, turned out to be the main thrust bearing. Install the crankshaft and bearings, torque to 15ftlbs hit the rear crankshaft flange with a mallet. This should even up the thrust bearing surfaces with the crankshaft. 65"
 
I had this issue on a 360 and it turned out the crank wieght was rubbing the oil pump. The casting had some extra material in that spot. Took a little material off and all was well.
 
Take one main cap off at a time rotate it and fid out which of the main bearings are tight and why.

Use something thick for assembly lube like STP or Lucus engine oil additive.
 
You could use a very light torque wrench and spin it snd see how much increase there is. I think you should be able to find a number that it should require to spin and then an amount at the completion of piston installation.
SBC would be around 15-25 ftlbs with the crank installed and 35-40 with the pistons in. Yes, old info, and relatively stock components, but the point is the same.
 
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Right on, back when NAPA main Tampa store had a machine shop, you could take em your stuff and Adam would check em out for ya really quick ( basic measurements, but by a Pro, with Pro tools) never charged for that, that don't tell ya everything, but for a build that was already running and a freshen up, it was a working deal
 
I agree with post #5 100%. You could do it like that, OR back up and untorque each cap until you find the offending cap. Either way will work. But isolating it will help your shop to track the problem down, or you might even get lucky and find and fix it yourself. I've found small nicks on the caps and block before that caused it, dressed them with a file and fixed it myself. I ain't skeered.
 
I took block and crank to machine shop and got it line honed and they checked crank for runout. The crank was fine but the block did in fact need a line hone. Put the crank back in and torqued mains to 50 ft lb no binding whatsover. Then went to 80 ft lb - no binding. Then went to 100 as per ARP instructions and it locks crank up tight - I cannot move it. Could the bearings be incorrect even though the part number is correct?. Because it is all stock I didn't measure
 
KosmicKuda said:
Another thing you could try is just setting the crank in the block without caps using upper bearing shells only in first and last saddles. Rig up a dial indicator and check for run out at other main journals.

Bent crank could be the reason for the spun bearing.
Click to expand...
That's the first thing I thought of.
 
When they line honed it, did they use the arp studs you’re using when you assemble it?
 
Plasti-Gauge them at 1/2 torque, then pull the caps and see which one is spreading out the Plasti-Gauge the widest. That will be where you problem lies. Oversize bearing issue . . .
 
Got back to looking at this 5.7 yesterday. I removed the crank and torqued all caps When I measured clearance t 80 ft pound I had .0025 clearance however when I Torque to 100 ft pounds I have .001 which is obviously to damn tight. I think when the line hone was done the caps were snugged down to 80 ft pounds. I will call the machine shop but I doubt they will remember. My question though is could I just leave them at 80 ft pounds. It has perfect clearance at this.
 
20220521_222713.jpg
 
Yep I know that most engines are around 80 - 85 however the ARP info says 100 with the studs. I think it will be fine at 80 though
 
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